Saliva has four main components that aid in digestion: mucus, amylase, lingual lipase, and electrolytes. It also contains proteins and enzymes like statherins, proline-rich proteins, histatins, cystatins, lysozyme, and salivary peroxidase. Saliva helps lubricate and protect tissues in the mouth from bacteria, aids in digestion of starches and fats, and regulates pH levels through bicarbonate ions. Its antimicrobial properties come from enzymes, histatins, cystatins, lysozyme, and peroxidase systems that inhibit bacterial growth and adhesion in the oral cavity.

1. Biochemistry of saliva Objectives Describe the composition of saliva Mention its functions Dr/ Ragaa Salama

2. Clinical Highlights Understanding of salivary mechanisms prerequisite for effective treatment of salivary gland dysfunctions modulation of bacterial colonization development of artificial saliva Dr/ Ragaa Salama

3. Saliva Definition : Secretions of salivary glands (parotid and submandibular/sublingual) Composition of Saliva : 4 major components 1-mucus that serves as a lubricant. 2-amylase ->initiates the digestion of starch. 3-lingual lipase -> begins digestion of fat. 4-electrolyte solution (Na+,Cl - , K+, HCO3 - -> moistens food. 5-proteins& enzymes: Statherins, Proline-rich Proteins (PRPs), Histatins, Cystatins, Lysozyme, Salivary peroxidase Dr/ Ragaa Salama

4. saliva is hypotonic to plasma -Na+ and Cl- ↓ in saliva than plasma -K+ and HCO3- ↑in saliva than in plasma. - pH changes from being slightly acidic (pH 6-7 ,at rest) to basic (pH 8) at ultimate stimulation ↑ ↑ HCO3- in the saliva -Amylase and mucus also increase in concentration after stimulation. Dr/ Ragaa Salama

5. functions of saliva Dr/ Ragaa Salama Salivary Families Anti- Bacterial Buffering Digestion Mineral- ization Lubricat- ion &Visco- elasticity Tissue Coating Anti- Fungal Anti- Viral Carbonic anhydrases, Histatins Amylases, Mucins, Lipase Cystatins, Histatins, Proline- rich proteins, Statherins Mucins, Statherins Amylases, Cystatins, Mucins, Proline-rich proteins, Statherins Histatins Cystatins, Mucins Amylases, Cystatins, Histatins, Mucins, Peroxidases

6. Mucin Functions Tissue Coating Protective coating about hard and soft tissues Primary role in formation of acquired pellicle Concentrates anti-microbial molecules at mucosal interface Lubrication Increases lubricating qualities (film strength) Aggregation of bacterial cells Bacterial adhere to mucins may result in surface attachment, or Mucin-coated bacteria may be unable to attach to surface Bacterial adhesion React with bacterial adhesins, thereby blocking them Dr/ Ragaa Salama

7. Amylases digestive function Hydrolyzes starches -> amylose ,amylopectin,Maltose ,glucose, in tears, serum, bronchial, and male and female urogenital secretions role in modulating bacterial adherence Dr/ Ragaa Salama

8. Lingual Lipase Secreted by von Ebner’s glands of tongue Involved in first phase of fat digestion Hydrolyzes medium- to long-chain triglycerides Important in digestion of milk fat in new-born highly hydrophobic enters fat globules Dr/ Ragaa Salama

9. Statherins Produced by acinar cells in salivary glands Statherins prevent precipitation or crystallization of supersaturated calcium phosphate in ductal saliva and oral fluid Lubricant. Dr/ Ragaa Salama

10. Proline-rich Proteins (PRPs) Inhibitors of calcium phosphate crystal growth Present in the initially formed enamel pellicle and in “mature” pellicles Acquired enamel pellicle is 0.1-1.0 µm thick layer of macromolecular material on the dental mineral surface Dr/ Ragaa Salama

11. Histatins A group of small histidine-rich proteins Potent inhibitors of Candida albicans growth Dr/ Ragaa Salama Cystatins Are inhibitors of cysteine-proteases protective against unwanted proteolysis (bacterial proteases, lysed leukocytes) inhibit proteases in periodontal tissues effect on calcium phosphate precipitation

12. Lysozyme ( LZ ) Present in numerous organs and most body fluids Oral LZ is derived from at least four sources major and minor salivary glands, phagocytic cells and gingival crevicular fluid (GCF) Biological function anti-microbial activity by: Inhibition of bacterial adhesion to tooth surfaces Inhibition of glucose uptake and acid production Muramidase activity (lysis of peptidoglycan layer) Dr/ Ragaa Salama

13. Salivary peroxidase systems Sialoperoxidase (SP, salivary peroxidase) Readily adsorbed to various surfaces of mouth enamel, salivary sediment, bacteria, dental plaque Myeloperoxidase (MP) From leukocytes entering via gingival crevice 15-20% of total peroxidase in whole saliva Dr/ Ragaa Salama

14. Regulation of oral microorganisms by SP/MP Dr/ Ragaa Salama Food Ingestion carbohydrates Stimulation Metabolism H + Recovery O 2 thiols Inhibition Salivary Glands SCN - + H 2 O 2 OSCN - /HOSCN Autoinhibition spontaneous +SP Unstimulated bacteria Inhibited bacteria Active bacteria

15. Other anti-microbial activities of LZ Muramidase activity (lysis of peptidoglycan layer) Cationic-dependent activation of bacterial autolysins Aggregation of bacteria Inhibition of bacterial adhesion to tooth surfaces Inhibition of glucose uptake and acid production Dr/ Ragaa Salama

16. Anti-microbial activities of saliva Dr/ Ragaa Salama

17. thiocyanate ions and another is several proteolytic enzymes— most important, lysozyme— that (a) attack the bacteria, (b) aid the thiocyanate ions in entering the bacteria where these ions in turn become bactericidal, and (c) digest food particles, thus helping further to remove the bacterial metabolic support. protein antibodies that can destroy oral bacteria Dr/ Ragaa Salama